(1) Field of the Invention
The present invention relates to a data processing unit and especially to an input/output interrupt system in a channel processing device situated between the input/output device and the central processing unit, for propagating an input/output interrupt from the input/output device to the central processing unit.
(2) Description of the Prior Art
In a conventional data processing device, an input/output device, i.e., a channel device, is formed so as to transmit data via a plurality of paths. However, in such data processing device, preparation for the transmission of data via an alternate path is usually effected by running the control program prepared in the central processing unit. Therefore, a constant time is required.
Due to the recent development of electronic apparatuses, the processing speed of a central processing unit, channel device, etc. is being increased more and more, enabling the electronic apparatuses to be operated more rapidly than conventional apparatuses. Therefore, the time which is required for input/output interrupt, the time which the central processing unit requires for preparation for the transmission of data via an alternate path, and the time which the channel device requires for activation of the input/output device via an alternate path, etc. is decreased as compared with a conventional apparatus.
Therefore, in the aforementioned data processing device, preparation for the transmission of data from the central processing unit via an alternate path is effected during internal initialization of the input/output device after activation via the channel device, that is, after the connection between the input/output device and the channel device is broken after input/output interrupt due to the busy state of the input/output device.
When the input/output device is initializing, the busy state thereof is reported as the central processing unit. Therefore, the alternate path assumes the same state as the primary path, and thus, the phenomenon of hang-up temporarily occurs and the efficiency is decreased.